I've only been using Source Mogul for a few weeks but it has already saved me so much time!! Search results are quickly returned and it is incredibly intuitive to use. Having used other product sourcing software in the past I am used to spending a large chunk of time deleting mismatching items, Source Mogul has high quality matching features and I have noticed very few mismatches (you can also choose to see items which may include more mismatches to find hidden gems if you so wish). The filter system is great, no more rerunning searches when you want to change your filters!
I truly believe Source Mogul is going to have a big impact on the Amazon FBA and FBM community.
The support from Ed and his team is second to none. They have also recently created a FB support community for their users to socialise and help each other, I recommend joining!